Cooling Towers
Cooling Towers for Cold Storage and Refrigeration Condensers
In cold storage the tower does not cool the product. It controls condensing pressure, and condensing pressure is most of your electricity bill.
What the tower is really controlling
On a cold storage plant the cooling tower never touches the product. It serves the condenser, and what it actually controls is condensing pressure.
That matters because compressor power rises steeply with condensing pressure. Every degree the condenser water runs warmer than it needs to shows up as compressor energy, every hour the plant runs, for the life of the installation.
A cold storage tower is therefore an energy decision far more than a comfort one, and the payback on getting it right is continuous rather than seasonal.
Working out the condenser load
The heat the tower must reject is the refrigeration duty plus the compressor work, which is why the condenser load is always larger than the plant tonnage.
For ammonia and common HFC systems on cold storage duty, total heat of rejection typically runs between 1.2 and 1.35 times the evaporator capacity, depending on suction temperature. A hard frozen store at low suction sits at the higher end because the compressor is working harder per ton.
Take that ratio from the compressor manufacturer data for your actual operating conditions rather than a rule of thumb, because the spread between a chilled store and a hard frozen store is significant.
Sizing for the season that matters
Cold storage plants run all year, which makes the design wet bulb choice more consequential than on a building that only cools in summer.
Size against the wet bulb your site genuinely reaches in the worst weeks, not an annual average. A tower that is comfortable in February and struggles in June will have the compressors labouring at high head pressure exactly when tariffs and ambient loads are worst.
Equally, resist specifying an unnecessarily tight approach. A tower sized for a 4 degree approach rather than 3 is meaningfully cheaper, and where the compressors are content with the resulting condenser temperature there is nothing to gain from the extra.
Scale on condenser tubes is the recurring problem
Condenser tubes are the hottest surfaces in the circuit, which makes them exactly where calcium carbonate prefers to deposit. Scale there acts as insulation, condensing pressure rises to compensate, and compressor energy rises with it.
The effect is gradual and easy to miss. Plants often accept a slowly climbing power bill as normal ageing when the actual cause is a millimetre of deposit that could have been prevented.
This is the application where non-chemical conditioning earns its place most clearly. It keeps the tubes clean without a dosing regime for the site to manage, and cold storage sites frequently have no water treatment staff at all.
Practical points for cold storage sites
A few things come up on nearly every cold storage project we work on:
- Plan for maintenance without a full shutdown. A store cannot simply stop, so multiple cells that can be isolated individually are worth the extra cost.
- Watch the noise. Many cold stores sit close to boundaries or residential roads, and fan noise is easier to design out than to retrofit.
- Keep the tower away from condenser discharge and other heat sources, so it draws genuinely ambient air rather than its own warm exhaust.
- Specify FRP construction. Cold store sites are wet, often coastal, and mild steel towers corrode quickly in that environment.
- Fit a working bleed line and check it. A blocked blowdown is the most common cause of scale we find on these plants.
Where to start
Send the refrigeration capacity, the suction and condensing conditions, the refrigerant, your location and the plot available. We will work the condenser load back from the compressor data and return a sized selection.
If the plant already exists and the power bill has been climbing, it is usually worth checking the condenser approach before assuming the compressors are tired.
